Creating Enums with getattr syntax.

gistfile1.py

'''
>>> Enum.Colors.red.green.blue()
<Enum: Colors>
 
>>> Colors.red
<Colors.red = 0>
>>> Colors.green
<Colors.green = 1>
>>> Colors.blue
<Colors.blue = 2>
'''

class MetaEnum(type):
    def __getattr__(cls, name):
        obj = type(name, (BaseEnum,), {})
        globals()[name] = obj
        return obj


class Enum(metaclass=MetaEnum):
    pass


class MetaBaseEnum(type):
    def __init__(cls, *args):
        type.__init__(cls, *args)
        cls._items = {}
        cls._cnt = 0
        cls._accept = True
        
    def __getattr__(cls, name):
        obj = cls._items.get(name)
        if obj:
            return obj
        if cls._accept:
            cls(name)
            return cls
        raise AttributeError(name)

    def __call__(cls, value=None):
        if value is None:
            cls._accept = False
            return cls
        else:
            return super().__call__(value)

    def __repr__(cls):
        return '<Enum: {}>'.format(cls.__name__)


class BaseEnum(metaclass=MetaBaseEnum):
    def __new__(cls, name):
        obj = cls._items.get(name)
        if obj is not None:
            return obj
        obj = object.__new__(cls)
        cls._items[name] = obj
        return obj
    
    def __init__(self, name):
        self.name = name
        self.val = type(self)._cnt
        type(self)._cnt += 1

    def __repr__(self):
        return '<{0.__class__.__name__}.{0.name} = {0.val}>'.format(self)